var divs = nav_2.children;
var bs = nav_2.getElementsByTagName("b");
var is = nav_2.getElementsByTagName("i");
var art = main.getElementsByTagName("article");
var as =nav_2.getElementsByTagName("a");
var as1 =nav_1.getElementsByTagName("a");
a1()
function a1() {
    for (var i = 1; i < divs.length; i++) {
        divs[i].onclick = function () {
            for (var i = 0; i < bs.length; i++) {
                divs[i + 1].lastElementChild.className = ""
                bs[i].className = "";
                is[i].className = "iconfont ";
            }
            var as = this.lastElementChild.children;
            this.firstElementChild.firstElementChild.nextElementSibling.className = "active";  // b标签 文本标题
            this.firstElementChild.firstElementChild.className = "iconfont active";  // 字体图标
            as1[1].innerText=this.firstElementChild.firstElementChild.nextElementSibling.innerText;
            this.lastElementChild.className = "active";  //span + -
            if (this.lastElementChild.className == "active") {
                for (var i = 1; i < divs.length; i++) {
                    divs[i].firstElementChild.lastElementChild.innerText = "+";
                }
                this.firstElementChild.lastElementChild.innerText = "-";
            }
        }
    }
    for (var i = 0; i < as.length; i++) {
        as[i].onclick = function () {
            for (var i = 0; i < as.length; i++) {
                as[i].className = "";
                art[i].style.display="none";
                as[i].setAttribute("xb", i);
            }
            as1[2].innerText=this.innerText;
            this.className = "active";
            i=this.getAttribute("xb");
            art[i].style.display="block";
        }
    }
}